International Union for Conservation of Nature and Natural Resources
(IUCN), is now known as World Conservation Union (WCU) whose headquarters are at Morges, Switzerland looks after the species which need protection. They maintain Red Data Book, which enlists the different categories of protection needed by flora and fauna.

Critically endangered organisms face an extremely high risk of extinction and hence, require a greater degree of conservation and care. Examples of such organisms include various species of mammals (rhinos), amphibians (frogs), etc.